Pe er Norton's Assembly Language Book for the IBM PC Other Brady Books by Peter Norton Inside the IBM PC, Revised and Enlarged MS-DOS and PC-DOS User' Guide PC-DOS: The Guide to High Performance Computing Pe r N rton's Assembly Language Book for the IBM PC Peter Norton and John Socha A Brady Book Published by Prentice Hall Press New York, New York 10023 Copyright © 1986 by Brady Communication Company, Inc. All rights reserved, including the right of reproduction in whole or in part in any form. Portions of this work were previou ly publi hed in a work ntitled: Assembly Language Safari On The IBM P A Brady Book Published by Prentice Hall Pre A Division of Simon & Schuster, Inc. Gulf + Western Building One Gulf + Western Plaza New York, New York 10023 PRENTICE HALL PRESS is a trademark of imon & chu ter, Inc. Manufactured in the United State of America 2 3 4 5 6 7 8 9 10 Library of Congress Cataloging-in-Publication Data Norton, Peter, 1943- Peter Norton's Assembly Language book for the IBM PC. "A Brady book." Includes index. 1. IBM Personal Computer-Programming. 2. Assembler language (Computer program language) I. Socha, John, 1958- . II. Title. III. Title: Assembly language book for the IBM PC. QA 76.8.l2594N66 1986 005.265 86-25363 ISBN 0-13-661901-0 Contents Part I Machine Language 1 Chapter 1 Debug and Arithmetic 3 Hexadecimal Numbers 4 Debug 4 Hexari thmetic 6 Converting Hexadecimal to Decimal 7 Five-Digit Hex Numbers 11 Converting Decimal to Hex 12 Negative Numbers 14 Bits, Bytes, Words, and Binary Notation 16 Two's Complemen~An Odd Sort of Negative Number 18 Summary 20 Chapter 2 8088 Arithmetic 21 Registers as Variables 22 Memory and the 8088 23 Addition, 8088 Style 26 Subtraction, 8088 Style 28 Negative Numbers in the 8088 29 Bytes in the 8088 29 Multiplication and Division, 8088 Style 31 Summary 34 Chapter 3 Printing Characters 35 INT-The Powerful Interrupt 36 A Graceful Exit-INT 20h 38 A Two-Line Program-Putting the Pieces Together 39 Entering Programs 40 MOVing Data into Registers 41 Writing a String of Characters 43 Summary 45 Chapter 4 Printing Binary Numbers 47 Rotations and the Carry Flag 48 Adding With the Carry Flag 49 Looping 50 Writing a Binary Number 53 vi C ntcnt Chapter 4 continued The Proceed Command 54 Summary 55 Chapter 5 Printing in Hex 57 Compare and Status Bits 5 Printing a Single Hex Digit 61 Another Rotate Instruction 64 Logic and AND 65 Putting It All Together 67 Summary 67 Chapter 6 Reading Character 69 Reading One Character 70 Reading a Single-Digit Hex Number 71 Reading a Two-Digit Hex Number 72 Summary 73 Chapter 7 Procedures-Cou in to ubroutine 75 Procedures 76 The Stack and Return Addresses 7 PUSH ing and PO Pping 79 Reading Hex Numbers with More Ease 1 Summary 4 Part II Assembly Language 85 Chapter 8 Welcome to the Assembler 87 A Program Without Debug 8 Creating Source Files 91 Linking 92 Back in Debug 93 Comments 94 Labels 94 Summary 96 Peter Norton's Assembly Language Book vn Chapter 9 Procedures and the Assembler 99 The Assembler's Procedures 100 The Hex-Output Procedures 103 The Beginnings of Modular Design 106 A Program Skeleton 107 Summary 107 Chapter 10 Printing in Decimal 109 Recalling the Conversion 110 Some Tricks 113 The Inner Workings 114 Summary 116 Chapter 11 Segments 117 Sectioning the 8088's Memory 118 Segment Pseudo-Ops 124 The ASSUME Pseudo-Op 126 Near and Far CALLs 127 More on the INT Instruction 129 Interrupt Vectors 131 Summary 132 Chapter 12 Course Corrections 133 Diskettes, Sectors, and Dskpatch 134 The Game Plan 136 Summary 138 Chapter 13 Modular Design 139 Separate Assembling 140 The Three Laws of Modular Design 144 Summary 147 Chapter 14 Dumping Memory 149 Addressing Modes 150 Adding Characters to the Dump 156 vm Content Chapter 14 continued Dumping 256 Bytes of Memory 15 Summary 163 Chapter 15 Dumping a Disk Sector 165 Making Life Easier 16 Format of the Make File 167 Patching up Disp_sec 16 Reading a Sector 169 Summary 174 Chapter 16 Enhancing the Sector Di pla 175 Adding Graphics Characters Adding Addresses to the Display Adding Horizontal Lines Adding Numbers to the Display Summary Part III The IBM PC's ROM BIOS 191 Chapter 17 The ROM BIOS Routin 193 VIDEO_IO, the ROM BIOS Routines 194 Moving the Cursor 199 Rewiring Variable Usage 201 Writing the Header 204 Summary 208 Chapter 18 The Ultimate WRITE_CHAR 209 A New WRITE_CHAR 210 Clearing to the End of a Line 212 Summary 215 Chapter 19 The Dispatcher 217 The Dispatcher 218 Reading Other Sectors 224 Philosophy of the Following Chapters 226